We propose to investigate the role of epileptic seizures in oxidative stress. There is a wealth of research that demonstrates epileptic seizures lead to the formation of reactive oxygen species (ROS), which cause oxidative damage to DNA, lipids, and proteins. We intend to investigate the role of excitotoxic catecholamine release during epileptic seizures and their role in the formation of ROS leading to oxidative stress. We will use microdialysis sampling in discrete brain regions along with simultaneous recording of electrocorticographic (ECoG) activity to probe chemical and electrographic activity changes in the brain associated with seizures. This will allow us to correlate biomarker levels with seizure activity. Microdialysis sampling will be used to continuously monitor several biochemical pathways prior to, during, and after induction of seizures. Microdialysis experiments will provide both temporal and spatial information about oxidative stress caused by seizures and the brains response to them. This dual approach will allow us to resolve questions that have remained unclear using plasma and urine sampling and standard tissue sampling techniques. Methods previously developed in the PI's laboratory will be used to monitor formation of ROS, biomarkers for DNA damage, and the neurotransmitter amino acids and catecholamines. New analytical methods will be developed to monitor aldehydes produced through lipid peroxidation, endogenous thiols and disulfides involved in protection from ROS, and prostanoids resulting from arachidonic acid metabolism. Initially, we will use a chemically-induced seizure model using 3-mercaptopropionic acid (3-MPA). Coupled to the advanced analytical methodology and microdialysis sampling, we will then investigate the neurological events leading from seizures to oxidative stress. In particular, the temporal relationship between oxidative stress (as measured by ROS formation), and neuroexcitation (as measured by the GABA/glutamate ratio and the catecholamines) will be determined and correlated to the duration and intensity of seizure episodes.